FRANKFURT—Federal Reserve Chairman Ben Bernanke, fielding a query from his Mexican counterpart on a panel discussion here Friday, said changes in exchange rates aren’t enough to bring balance to the world economy.

Pressed by Agustin Carstens, his Mexican counterpart, Mr. Bernanke said, “I don’t think exchange rates by themselves can restore balances,” Mr. Bernanke said. The Fed has been accused, abroad and at home, of deliberating seeking to depress the value of the dollar by, effectively, printing $600 billion to buy long-term Treasurys. Mr. Bernanke insists that isn’t his objective. His and others’ textbooks observe, though, that any move to ease credit by a central bank tends to reduce the value of its currency.

In a panel discussion at a European Central Bank conference, Mr. Bernanke acknowledged uncertainty about the potency of the Fed’s move. “We don’t know how much impact there will be on activity,” he said, “but we think it will be meaningful.” He described himself as “skeptical” about claims the Federal Reserve might be “pushing on a string” by easing monetary policy at a time when U.S. households are trying save more and reduce their debts.

At the conference, ECB President Jean-Claude Triche reiterated his endorsement of U.S. authorities’ oft-stated view that a strong U.S. dollar is in the national interest. “A solid, strong U.S. dollar—one that is credible vis-a-vis other currencies—is very, very important,” Mr. Trichet said.

Dominique Strauss-Kahn, managing director of the International Monetary Fund, said on the same panel that “the currency question is only part of the problem.”

In a formal speech at the ECB conference earlier Friday, Mr. Bernanke lashed out at fast-growing economies that weren’t letting their currencies appreciate, saying they risked creating a “two-speed” global economy.

In the panel discussion, the Fed chairman cited a joke wherein national authorities solemnly pledge to their foreign counterparts to take care of their own currency’s exchange rates if only the others would do the same, and said the same could be applied to current-account surpluses and deficits. Officials in some other countries, he said, appear to insisting that the U.S. narrow its trade deficit by boosting national savings without acknowledging their own role in making that task easier or harder, Mr. Bernanke said.

Mr. Bernanke, partly in response to Henrique Meirelles, the Brazilian central banker, emphasized that not all emerging economies were managing their currencies or restraining domestic demand.

And in an indirect response to criticism that the Federal Reserve’s quantitative easing is funneling excess liquidity into emerging markets and thereby causing strains, Mr. Bernanke suggested that “spillovers of emerging markets on other emerging markets require more attention.”

Mr. Meirelles had noted that Brazil’s current-account deficit could widen by more than 60% next year to around $67 billion from around $39 billion this year, a trend that could raise concerns if sustained over the longer term.

Mr. Bernanke said central banks around the world during global financial crisis follow advice that dates to 19th-century British economist Walter Bagehot’s precept to “lend freely” in times of distress. But Mr. Bagehot’s advice came at a time that when national authorities had to worry about gold inflows and outflows, and they “certainly didn’t have to think about coordinating policy with foreign central banks,” Mr. Bernanke said.

About Real Time Economics

Real Time Economics offers exclusive news, analysis and commentary on the U.S. and global economy, central bank policy and economics. Send news items, comments and questions to the editors and reporters below or email realtimeeconomics@wsj.com.